This invention relates to an electronic watermarking system of a type jointly using a scramble effect, particularly to an electronic watermarking system which inserts a watermark into data and adds an scramble effect thereinto for the purpose of protecting a copyright, or the like.
Recently, an electronic watermarking system comes to be used for authenticating copyright ownership, identifying copyright infringers, or transmitting a hidden message.
As a conventional example of such an electronic watermarking system in which electronic watermarking data are embedded into a digital image, a proposal is made for a method of inserting electronic watermarking data in Nikkei Electronics, No. 660 published Apr. 22, 1996, Page 13. In the proposal, an image is converted into frequency components and the electronic watermarking data are embedded into an area having strong frequency components in an image signal after frequency conversion. The method disclosed therein is such a method for inserting ID information into digital works of which an object is a moving picture, a static picture,. a photograph, or a voice. In the method, the ID information is inserted per every buyer of the digital work so as to be used in a case that a digital work illegally copied by a person other than the buyer should be prosecuted. Further, another conventional method is also proposed, in which an improvement is made particularly for image processing systems using MPEG.
However, as will later be described more in detail, it is not enough in the conventional methods to provide digital image data with high secrecy.
It is therefore an object of the present invention to provide an electronic watermarking system which is capable of providing image data with very high secrecy.
Other objects of the present invention will become clear as the description proceeds.
According to an aspect of the present invention, there is provided an electronic watermarking device which is for use in inserting an electronic watermark into an original image consisting of a plurality of primary blocks, comprising: first discrete cosine transform means for carrying out first discrete cosine transform of at least one of the a plurality of primary blocks; inserting means for inserting electronic watermarking data into an output of the first discrete cosine transform means; inverse discrete cosine transform means for carrying out inverse discrete cosine transform of an output of the inserting means; and first coordinate converting means which have first coordinate conversion data and which carry out first coordinate conversion of an output of the inverse discrete cosine transform means by the electronic watermarking data and the coordinate conversion data.
According to another aspect or the present invention, there is provided an electronic image reproducing device which is for use in reproducing an original image from an electronic watermarked image consisting of a plurality of secondary blocks, comprising: second discrete cosine transform means for carrying out second discrete cosine transform of at least one of the a plurality of secondary blocks; extracting means for extracting electronic watermarking data from an output of the second discrete cosine transform means; extracted data containing means for containing an output of the extracting means; correspondence detecting means which compare an output of the extracted data containing means with an original electronic watermarking data to detect whether or not the output of the extracted data containing means is corresponding with the original electronic watermarking data; output image switching means which output the electronic watermarked image when the output of the extracted data containing means is detected to be not corresponding with the original electronic watermarking data by the correspondence detecting means, and first inverse coordinate converting means which have first inverse coordinate conversion data and which carry out first inverse coordinate conversion of the output of the extracted data containing means with reference to the original electronic watermarking data and the first inverse coordinate conversion data when the output of the extracted data containing means is detected to be corresponding with the original electronic watermarking data by the correspondence detecting means.
According to still another aspect of the present invention, there is provided an electronic watermarking system which is for use in inserting an electronic watermark into an original image consisting of a plurality of primary blocks, comprising: inserting means for inserting electronic watermarking data into at least one of the a plurality of primary blocks; second coordinate converting means which have second coordinate conversion data and which carry out second coordinate conversion of an output of the inserting means by the electronic watermarking data and the second coordinate conversion data; extracting means for extracting electronic watermarking data from a part of the coordinate-converted electronic watermarked image; and second inverse coordinate converting means which have second inverse coordinate conversion data and which carry out second inverse coordinate conversion of the output of the extracting means with reference to the original electronic watermarking data and the second inverse coordinate conversion data when the output of the extracting means is corresponding with the original electronic watermarking data.
The electronic watermarking data may be identical with the original electronic watermarking data, the second coordinate conversion data may be identical with the second inverse coordinate conversion data.
The second coordinate converting means may calculate a coordinate of one of the primary blocks outputted from the inserting means by the electronic watermarking data and the second coordinate conversion data, the coordinate being occupied within a region where an image having the inserted electronic watermarking data is contained.
One primary block may consist of 8xc3x978 elements, the second coordinate conversion being carried out by converting one block coordinate into another block coordinate in a frame.